This reminds me of Chrome, which switched from the original 3D logo to a flat logo back in 2011. "We're working on refreshing the icon to better represent the speed and simplicity of the modern browser and operating system," said Google at that time.

Update: The Verge reports that "a person familiar with Google's branding [says that] this is not a replacement for the company's traditional logo. Instead, the flatter design is used in instances where the beveled logo may not display well — such as on printed banners or other corporate use cases."